[gthumb] shortcut editor: make it clear that some shortcuts cannot be changed

[Paolo Bacchilega <paobac src gnome org>]

commit 86c7748b782b5b2a915398752d365b8ba673d064
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Fri Nov 22 10:24:18 2019 +0100

    shortcut editor: make it clear that some shortcuts cannot be changed

 gthumb/gth-window.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/gthumb/gth-window.c b/gthumb/gth-window.c
index 0d8a3452..247a31b9 100644
--- a/gthumb/gth-window.c
+++ b/gthumb/gth-window.c
@@ -1042,9 +1042,14 @@ gth_window_can_change_shortcut (GthWindow         *window,
                GtkWidget *dialog;
 
                label = gtk_accelerator_get_label (keycode, modifiers);
-               msg = g_strdup_printf (_("The key combination «%s» is already assigned to the action «%s»."),
-                                      label,
-                                      shortcut->description);
+               if (shortcut->description != NULL)
+                       msg = g_strdup_printf (_("The key combination «%s» is already assigned to the action 
«%s» and cannot be changed."),
+                                              label,
+                                              shortcut->description);
+               else
+                       msg = g_strdup_printf (_("The key combination «%s» is already assigned and cannot be 
changed."),
+                                              label);
+
                dialog = _gtk_message_dialog_new (parent,
                                                  GTK_DIALOG_MODAL | GTK_DIALOG_DESTROY_WITH_PARENT,
                                                  _GTK_ICON_NAME_DIALOG_ERROR,